This application is based on Patent Application No. 10-219449 (1998) filed Aug. 3, 1998 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ejection recovery system and an ejection recovery method for a liquid ejection head, such as an ink-jet printing head or the like, to be mounted on an ink-jet printer, a plotter and so on, for performing printing by ejecting liquid, such as ink or the like, on a printing medium.
2. Description of the Related Art
Conventionally, as a printing system performing printing on a printing medium, such as paper, cloth, a plastic sheet, an OHP sheet or the like (hereinafter simply referred to as printing paper), there have been know various printing systems, such as a wire-dot system, a thermal printing system, a heat transfer system, an ink-jet system and so on. Among these systems, a printing apparatus employing the ink-jet system (hereinafter referred to an ink-jet printing apparatus) has been used and commercialized as output means of an information processing system, such as a printer as a copy terminal, or a handy type printer or a portable printer which can be connected to a personal computer, a host computer, a disk drive device, a video device or the like.
In the printing head to be employed in the above-mentioned ink-jet printing apparatus, energy generation elements for generating energy for ejecting ink from ejection openings are provided. As the energy generation element, there are one using an electromechanical transducer, such as a piezoelectric element, one generating heat by irradiating an electromagnetic wave, such as a laser for ejecting an ink droplet by action of the generated heat, one heating liquid by an electrothermal transducer having a heating resistor for ejecting the ink droplet, or so on.
On the other hand, for an ink-jet printing apparatus, outputting of a color image has been required for advancement of softwares and a computer in the recent year. Adapting to such situation, the ink-jet printing head is also adapted for color printing. Currently, a multi-color head has been typically realized by combining a plurality of single color heads. Also, through certain head manufacturing process, a multiple color head is present.
In addition to colorizing, higher printing density in outputting of an image has been demanded. By densification of printing density in the ink-jet system or using different ink densities, formation of higher density and higher quality of image is attempted to realize.
Then, in order to form a high density and high quality image, it has been attempted for further densification of arrangement pitch of ink ejection openings and for down-sizing of ink droplets to be ejected from the ink ejection openings by making an opening area of each ink ejection opening much smaller.
On the other hand, in the case where the multi-color head is formed by combining single color heads set out as one means for adaptation for colorizing, down-sizing of the single color head is inherent. As a result, an ink chamber formed within the head is inherently down-sized.
In the background set forth above, the entire head including the ink ejection openings and the ink chamber is inclined to be down-sized. A pre-shipment step after production of the head, an ink filling-up operation or recovery operation to the ink chamber and ink passages of the head to be mounted on an ink-jet printer or an ink-jet plotter has been performed by covering overall an ink ejection opening forming surface, with a cap formed of flexible material, and introducing vacuum within the cap for sucking the ink.
Here, a recovery cap and a recovery operation to be employed for the conventional ink-jet printing head will be explained.
FIGS. 9A and 9B show recovery cap C to be used for recovery operation of the conventional ink-jet printing head, wherein FIG. 9A is a plan view of the recovery cap C and FIG. 9B is a section taken along line IXBxe2x80x94IXB of FIG. 9A. The recovery cap C is generally constructed with an substantially plate-like cap guide 30, rubber caps 31a and 31b respectively fitted in two recessed portions 30a and 30b of the cap guide 30. The rubber caps 31a and 31b are respectively formed with suction holes 32a and 32b at substantially central portions. The suction holes 32a and 32b are generally formed with hole portions 30c and 30d respectively formed in the recessed portion 30a (not shown) of the cap guide 30 and in central bottom portion of the recessed portion 30b, and hole portions 31c and 31d communicated with the hole portions 30c and 30d and respectively formed in the central bottom portions of the rubber caps 31a and 31b. The rubber caps 31a and 31b are formed of a rubbery elastic material, such as a silicone rubber or a butyl rubber. Respective projection contours E of the rubber caps 31a and 31b are formed projecting from plain of the cap guide 30. Therefore, as shown in FIG. 10, when the rubber caps 31a and 31b abut on the ink ejection opening forming surface, a space defined therebetween can be a sealed space by elastic deformation of the projection contours E. The sealed space is sucked by a suction pump (not shown) via a tube 40 connected to the suction holes 32a and 32b. Sucked ink is discharged to a waste ink holder (not shown).
A relationship between the conventional ink-jet printing head and the recovery cap is downwardly oriented the ink ejection opening forming surface, of the former, and upwardly oriented the recovery cap opposing to the ink ejection opening forming surface. This condition is illustrated in enlarged form in FIG. 11A.
FIG. 11A is an enlarged section showing an abutting condition of the ink cartridge and the recovery cap in FIG. 10. The projecting contours E of the recovery caps abut onto the ink ejection opening forming surface, to define the inside of the projecting contours E as sealed space D for effectively transmitting a suction force F to ink passages 41 and an ink chamber 42.
FIG. 11B is an enlarged section showing a condition where recovery operation for filling-up ink into the ink chamber and the ink passages from the condition where the ink cartridge and the recovery cap abut. Here, for bubble J present in a condition where meniscus is formed within the ink passage 41, bubble K present in a condition blocking the ink passage, and bubble M present in unspecified size within the ink chamber 42, suction recovery operation is performed for removing these bubbles by the suction pressure F. Then, upon removal of bubbles, for the ink passages where bubble J and bubble K reside, suction has to be performed by shown acting pressures O1 to O4 in consideration of a damper effect and a meniscus force of bubbles. However, in the ink passages where no bubble is present, suction is effected even by acting pressure N much smaller than the acting pressures O1 to O4. Accordingly, by the suction recovery operation, ink is directly sucked from the ink passages where no bubble is present. From the ink passages where a bubble is present, suction of the ink is difficult. Therefore, a large amount of ink should be sucked and drained in order to remove all of bubbles.
Problems in the conventional ejection recovery system is summarized as follows.
(1) In an ink-jet printing head, an ink droplet is formed by ejecting a necessary amount of ink filled in an ink passage with rupturing a meniscus formed in an ink ejection opening. Then, when filling-up of ink into ink passages and an ink chamber is to be performed by introducing a reduced pressure within a cap sealingly covering overall an ink ejection opening forming surface, a meniscus force generated in the ink ejection opening for small opening area of the ink ejection opening associating with demand for higher quality and higher definition of image required in the recent years, becomes large to require large suction pressure.
On the other hand, when suction is performed for an ink-jet head in a condition where ink passages filled with ink and an ink passages not fully filled with ink are present in an admixing manner, loss of suction pressure due to a damper effect of air layers within the ink passage, in which ink is not fully filled, becomes significantly large. As a result, a great amount of ink is sucked unnecessarily from the ink passage which has already been fully filled with ink.
(2) On the other hand, an ink chamber supplying ink into ink passages is small and complicate in shape associating with down-sizing of an ink-jet head. Therefore, even when recovery operation by suction is performed, air in the ink chamber (hereinafter called as a bubble) is difficult to be removed. This phenomenon is a condition where a contact angle of the ink in the ink passages and the ink chamber becomes large, namely so-called wetting ability is low,. This problem is particularly significant before aging processing during ink-jet head production process or before shipping inspection printing.
(3) Moreover, in the case of an ink-jet head which can be mounted in a label printer or the like and has a long ink ejection opening array, since number of ink ejection openings is large, an ink suction amount may be increased when a damper effect is generated in a portion where ink is not fully filled.
It is a first object of the present invention to provide an ejection recovery system and method which enable an ink filling-up operation without causing residual of bubbles in an ink chamber and ink passages before aging processing during a head production process and shipping inspection printing, for an ink-jet printing head to be loaded in an ink-jet printer, plotter or the like to perform printing by ejecting ink onto a printing medium.
It is a second object of the present invention to provide an ejection recovery system which can be installed in a plotter, a large size printer or the like, in which volumes are not so limitative, in addition to use in a factory shipment process, such as aging processing and shipping inspection printing.
In the first aspect of the present invention, there is provided an ejection recovery system for a liquid ejection head including ejection openings for ejecting liquid, liquid passages communicated with the ejection openings, and ejection energy generating elements provided in the liquid passages and generating energy sufficient for ejecting the liquid, comprising:
a cover member having a cover opening for covering at least one of the ejection openings and contacting with a surface including the ejection openings of the liquid ejection head arranged for orienting the surface including the ejection openings upwardly; and
suction means for generating a vacuum pressure introduced into a space defined by the cover member and the surface including the ejection openings and for performing suction from the at least one of the ejection openings covered by the cover member through the cover opening.
Here, when a diameter of a cover opening of the cover member is L1 and a length of an array of the ejection openings aligned in a row is L2, a relationship of L1 less than L2 may be established, and the system further comprises moving means for relatively moving the cover member and the surface including the ejection openings of the liquid ejection head in a direction of length of the array of the ejection openings. With the construction set forth above,a recovery operation can be effected only for a part of the ink ejection opening array where a recovery operation is required, concentrically.
On the other hand, an ejection recovery system may further comprises ultrasonic wave generating means for applying an ultrasonic wave to the liquid ejection head when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head by the suction means. By providing the ultrasonic wave generating means, it becomes possible to grow bubbles into greater size and make bubbles to be easily released from walls of the liquid passages and the liquid chamber.
Furthermore, the liquid ejection head may be placed in an environmental atmosphere at a temperature in a range of about 35xc2x0 C. to 80xc2x0 C., when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head by the suction means. By varying temperature environment, bubbles can be moved effectively.
On the other hand, the ejection recovery system may further comprise an energy generating element for temperature adjustment provided in the liquid passage of the liquid ejection head for adjusting the liquid at a predetermined temperature, and a temperature of the liquid ejection head is adjusted in a range of about 35xc2x0 C. to 60xc2x0 C. by driving the temperature adjusting energy generating element, when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head by the suction means. By varying temperature environment, bubbles can be moved effectively.
Furthermore, the cover member may have flexibility. In such case, it is preferred that a material of the cover member is selected among Si type rubber and Bu type rubber. Here, rubber material containing Si is included in the Si type rubber and rubber material containing butyl group is included in Bu type rubber.
On the other hand, the ejection recovery system may further comprise monitoring means for optically monitoring a condition of the liquid passage and a liquid chamber communicated with the liquid passage in the liquid ejection head, and suction by the suction means may be performed again when the liquid passage and the liquid chamber in the liquid ejection head as monitored by the monitoring means are not filled with the liquid. By this, judgment whether re-suction is required or not can be performed per the each of liquid passages, so that re-suction can be performed locally and concentrically only for the liquid passages which have been judged as re-suction is necessary in a short period, resulting in extinguishing residual bubbles at early timing.
On the other hand, the ejection energy generating means may be a thermal energy generating element generating a thermal energy sufficient for ejecting the liquid. The temperature adjusting energy generating element may be a thermal energy generating element for generating a thermal energy sufficient for heating the liquid.
In the ejection recovery system according to the present invention constructed as set forth above, since the cover member contacting with a surface including the ejection openings of the liquid ejection head arranged for orienting the surface including the ejection openings upwardly and suction means for introducing a vacuum pressure into a space defined by the cover member and the surface including the ejection openings, the vacuum pressure is introduced into the space in a condition where bubbles presenting in the liquid passages are floating up toward the ejection openings to effectively discharge bubbles toward the clearance.
On the other hand, since a diameter of a cover opening of the cover member is L1 and a length of an array of the ejection openings aligned in a row is L2, a relationship of L1 less than L2 is established, suction pressure can be concentrically applied with the cover member abutting and moving along the longitudinal direction of the ink ejection opening array without being influenced by overall bubbles even if bubbles are present. Thus, it becomes possible to perform an effective recovery operation with the least necessary suction amount of the liquid without sucking and draining significantly a large amount of liquid in recovery operation to be performed before aging processing or before shipping inspection printing in the head manufacturing process. On the other hand, when the number of ejection openings is large, since an unnecessary suction amount of the liquid can be reduced, particularly effective filling up of the liquid, namely, refilling, can be performed.
It is further preferred that, assuming that a sectional area of a cover opening of the cover member is S1 and summation of areas of the ejection openings covered by the cover opening is S2, a relationship
10,000xe2x89xa7S1/S2xe2x89xa710
is satisfied.
On the other hand, it is also preferred that, assuming a diameter of the cover opening of the cover member is L1 and a length of the array of the ejection openings aligned in a row is L2, a relationship
1 less than L2/L1xe2x89xa6500
is satisfied.
In the second aspect of the present invention, there is provided an ejection recovery method for a liquid ejection head including ejection openings for ejecting liquid, liquid passages communicated with the ejection openings, and ejection energy generating elements provided in the liquid passages and generating energy sufficient for ejecting the liquid, comprising the steps of:
arranging a surface including the ejection openings orienting upwardly;
contacting a cover member having a cover opening for covering at least one of the ejection openings onto the surface including the ejection openings of the liquid ejection head from above; and
performing suction from the at least one of the ejection openings covered by the cover member through the cover opening by a vacuum pressure introduced into a space defined by the cover member and the surface including the ejection openings.
Here, assuming a diameter of a cover opening of the cover member being L1 and a length of an array of the ejection openings aligned in a row being L2, a relationship of L1 less than L2 is preferably be established, and the method further may comprise a step of relatively moving the cover member and the surface including the ejection openings of the liquid ejection head in a direction of length of the array of the ejection openings.
The method may further comprise a step of applying an ultrasonic wave to the liquid ejection head when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head.
The method may further comprise a step of placing the liquid ejection head in an environmental atmosphere at a temperature in a range of about 35xc2x0 C. to 80xc2x0 C., when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head.
On the other hand, the method may further comprises a step of driving an energy generating element for temperature adjustment provided in the liquid passage for adjusting a temperature of the liquid ejection head in a range of about 35xc2x0 C. to 60xc2x0 C., when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head by the suction means.
The method may further comprise a step of optically monitoring a condition of the liquid passage and a liquid chamber communicated with the liquid passage in the liquid ejection head, and performing suction again when the liquid passage and the liquid chamber in the liquid ejection head as monitored are not filled with the liquid.
In the third aspect of the present invention, there is provided a liquid ejection printing apparatus performing printing by ejecting liquid to a printing medium from a liquid ejection head including ejection openings ejecting liquid, liquid passages communicated with the ejection openings and ejection energy generating elements provided in the liquid passages and generating energy sufficient for ejecting the liquid, comprising:
a carriage for mounting the liquid ejection head;
an ejection recovery system including a cover member having a cover opening for covering at least one of the ejection openings and contacting with a surface including the ejection openings of the liquid ejection head arranged for orienting the surface including the ejection openings upwardly and suction means for generating a vacuum pressure introduced into a space defined by the cover member and the surface including the ejection openings and for performing suction from the at least one of the ejection openings covered by the cover member through the cover opening; and
changing means for changing a direction of the carriage for orienting the surface including the ejection openings of the liquid ejection head upwardly.
Here, when a diameter of a cover opening of the cover member is L1 and a length of an array of the ejection openings aligned in a row is L2, a relationship of L1 less than L2 may be established, and the system further comprises moving means for relatively moving the cover member and the surface including the ejection openings of the liquid ejection head in a direction of length of the array of the ejection openings.
On the other hand, an ejection recovery system may further comprises ultrasonic wave generating means for applying an ultrasonic wave to the liquid ejection head when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head by the suction means.
Furthermore, the liquid ejection head may be placed in an environmental atmosphere at a temperature in a range of about 35xc2x0 C. to 80xc2x0 C., when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head by the suction means.
On the other hand, the ejection recovery system may further comprise an energy generating element for temperature adjustment provided in the liquid passage of the liquid ejection head for adjusting the liquid at a predetermined temperature, and a temperature of the liquid ejection head is adjusted in a range of about 35xc2x0 C. to 60xc2x0 C. by driving the temperature adjusting energy generating element, when vacuum pressure is introduced into the space defined by the cover member and the surface including the ejection openings of the liquid ejection head by the suction means.
As set forth above, in accordance with the present invention, by abutting and sucking the liquid ejection opening forming surface of the liquid ejection head oriented upwardly, from the above by the elastic member provided with the suction hole, bubbles residing within the liquid passages and floating up to the ejection openings can be effectively sucked out.
On the other hand, by making the internal diameter of the suction hole of the elastic member smaller than the length of the ejection opening array, a part of the ejection opening array can be concentrically sucked to omit suction operation for the ejection openings which do not require recovery.
Furthermore, by relatively moving the elastic member and the ejection opening array, even if bubbles are present, it becomes possible to concentrically apply the suction pressure without being influenced by all of bubbles. Therefore, an effective recovery can be performed with the least necessary ink suction amount without sucking and draining a significantly large amount of ink during a recovery operation before aging processing or before shipping inspection printing in the ink-jet head manufacturing process.
On the other hand, when the number of the ejection openings is large, particularly effective ink filling up can be performed for reduction of an unnecessary ink suction amount.
Furthermore, the ejection recovery system according to the present invention is applicable not only for pre-factory shipment process, such as aging processing or shipping inspection printing, but also as the ejection recovery system to be mounted in a plotter, a large size printer or the like which has smaller constraint in a size of a main body to prevent user from draining unnecessarily a large amount of the ink and thus to contribute for ecology.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.